Quote:
Originally Posted by ChazInMT
I was planning on setting my circular saw to 1/8 inch deep and making kerfs in the back in the direction (or two) that I wanted the wood to bend. I know it isn't the best way to do it but I don't think it will affect the strength that much if I fasten it well. This is just a "proof of concept" cap anyway. I'll be happy to use it until June. So epoxy coating is not really a priority. If it significantly improves my mileage on the road, I'll make a more robust version with some kind of hatch back door thing and windows.
I'm fairly convinced that this is a good direction to start with by tapering in the sides and having a curved arch top profile. Most folks don't taper the sides and I think really only end up improving the airflow over 2 or 3 feet down the centerline of the truck bed. By taking the time to do this, I'm managing all the air above the bed which is about 8 linear feet of the slipstream (22" tall sides + 52" wide roof). After reading a bunch of technical papers today over in the "General Efficiency" forum, I'm getting a little concerned about lift forces that might be generated at highway speeds (with a head wind, passing a truck and 82% humidity). I don't think it will significantly affect handling, I just worry that the cap will come loose and take a short flight. I'm going to double the hold down system I was originally planning to avoid having to fill out a EAA membership, although I'm certain Burt Rutan would love having me in the ranks.
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The cap will "explode" if not strong enough to withstand the delta-p across it.
And it would "leave" if allowed,so good idea on extra hold downs.
The plan-view curvature will cut extra drag.You'll experience a bit of cross-talk where the rails and cap meet.It cannot be avoided short of a bed re-design.Kamm suffered this on his K-cars,don't worry about it.
As far as bow shock-waves from 18-wheelers,etc.,she should be rock-solid.The cap will provide you downforce and you'll swear there's a load in the bed the way she rides.
Put in a Plex side window on the passenger side if you can.Backing out of a parallel parking space can be terrifying without it.
Even a slit at the rear will also give you some vision you'll enjoy.
Tensile strength is your friend.
P.S.If you're going anywhere near goats,make it VERY strong!